This invention relates to alginate dental impression materials used for taking an impression of dentition and surrounding oral tissues. The primary object of the invention is to prevent dental impressions formed from alginate impression materials from spreading infectious disease organisms by providing biocidal properties.
For many years health care professionals have been concerned that their patients may be cross-infected with microorganisms from a diseased patient. To minimize this risk, they sterilize their instruments by autoclaving or ethylene oxide treatment, wear face masks and gowns, and exercise scrupulous cleanliness in their operating rooms and offices.
Dentistry poses an especially more accentuated risk to the health-care profession because the surgical field is the oral cavity which contains many strains of bacteria. Dental operations spread these throughout the orifice atmosphere, thereby exposing dentists and dental auxiliaries to possible infection. In recent years concern has deepened over spreading viral infections such as Hepatitis B, A.I.D.S., and herpes.
Despite dentists' best efforts to sterilize their instruments and hardware, there are certain sensitive dental materials which have heretofore been difficult and in some cases impossible to sterilize, because the heat or chemicals needed for sterility would adversely affect the material's primary function. Dental impression materials are an example of this--their primary function is to make an accurate replica of the oral tissues and thus they must be rubbery, dimensionally accurate and have good surface wetting properties. Any application of heat or unusual chemical activity to achieve sterility can cause them to distort, soften, stick to teeth and other surfaces or otherwise defeat their main purpose. This is especially a problem for alginate impressions which are hydrogels of calcium alginate and inert filler. These compounds can dehydrate rapidly, thus changing dimension; or if placed in an aqueous sterilizing solution they attract additional water, thus also changing dimension. As a consequence, normal dental impressions become contaminated or impregnated with bacteria and viruses from the patient, which can be spread to dental auxiliaries (assistants, technicians) who handle the impressions in the process of making casts, models and prosthesis.
It is known in the dental art that hydrocolloid materials of the agar type are kept in a warm condition between uses and thus provide ideal conditions for mold growth. It is a common practice to add a chemical preservative or fungicide to prevent such mold growth.
It also is known that hydrophilic polymer containing powders and pastes may be used as denture adherents and that the addition of antimicrobial agents may make an individual patient's denture more sanitary or less prone to offensive odor.
However, neither of the above prior art examples are intended to prevent cross-infection of disease organisms, nor do they apply to the alginate type of irreversible hydrocolloid impression material.
Some dental impression materials, such as silicone rubbers, are hydrophobic and relatively impervious to oral fluids and may be partially decontaminated by surface treatment, such as wiping with alcohol or immersing in an aqueous biocidal material. However, alginate impression materials are preferred for partial dentures, orthodontics, and many other dental procedures. These alginate impression materials are particularly prone to contamination because oral fluids may diffuse into them and remain unaffected by brief surface treatment. When formed into the impression the alginate materials tend to swell and distort if immersed in aqueous disinfectants or when the surfaces of the impression are treated.